The invention which has a very extensive field of applications, is especially associated with the replacement/maintenance/repairing of instruments at critical locations and/or places difficult of access and/or within risky surroundings.
The invention is particularly adapted for subsea applications and may, advantageously, be used when replacing instruments incorporated into or being associated with subsea installations.
The major advantages of the tool device, the instrument housing the locking tool, and the method according to the invention will, however, likewise be obtainable in instrument replacements within low/high pressure systems wherein circulation of inflammable and/or explosive and/or corrosive fluids takes place.
Moreover, the invention may, advantageously, be utilized in, for example, a radioactive environment wherein the replacement of the instrument is effected by means of a robot arm.
However, the fields of application of the present invention defined in the foregoing are to be considered as non-limiting examples only, a number of further applications being conceivable besides the particularly mentioned ones.
The instrument or another device to be replaced by means of the invention, may fundamentally be any kind of instrument or another device and will be indicated as "instrument" only in the following. However, as should be mentioned, the housing of this instrument according to the present invention is presupposed to be intact during and after the replacement operation, and that this instrument housing according to the invention is formed partly in order to enable locking of the instrument from withdrawal/pushing-out in the operative positions thereof (e.g. open/closed), partly in order to allow the withdrawal/pushing-out of the instrument from the instrument housing for replacing it with a new identical instrument as soon as said withdrawal-preventing locking has been neutralized.
As associated with this invention, the term device/instrument comprises i.a. all kinds of valves, especially instrumentation valves, wherein the instrument housing according to the present invention is maintained during/after the replacement operation; a large number of transducers such as pressure transducers, temperature transducers, signal and measuring transducers; a plurality of various sensor devices, as well as flow measuring instruments, all having a corresponding housing design. In each single case, said valves, transducers, sensors and measuring instruments are mounted at critical locations and/ or in places difficult of access, e.g. in subsea or risky surroundings.
As a concrete example of the practical use of the invention within the oil industry may be mentioned the replacement of a high pressure valve (a ball valve) installed on a well frame at large sea depths, and in the following, the invention will substantially be described in connection with such a valve replacement. Such a high pressure ball valve would be coupled into a flexible hydraulic control line, which may lead to another (main) valve incorporated into a blowout preventer or a so-called Christmas tree.
In order to effect replacement of such a valve according to conventional or technique, the valve has to be opened or demounted by divers, leaving the hydraulic control line open during the replacement operation. This will inevitably result in the possibility of leakage of the medium (high pressure oil) within the control line, a very disadvantageous effect per se. However, substantially more undesirable is the fact that the open control line allows entry of sea water, forming a source of contamination of a substantial size.
When a control line has been contaminated by sea water in this manner, a cleaning and flushing process must be carried out until desired cleanness of the control line has been achieved. Such a cleaning and flushing process in order to remove sea water from the control line, is simply defined as "purging" within the area in question, and one gets an impression of how time-consuming and cumbersome such a process may be, when it is mentioned that such hydraulic control lines to be "purged" may have a length of 10-20 kilometers.
Prior art technique for the replacement of other instruments, e.g. pressure sensor instruments of transducer type, comprises mounting of a plurality of identical instruments, side by side, at each single measuring point. Thereby, one may avoid cumbersome diving operations; an error or failure in one instrument being correctable through the switching-over to another, intact instrument. The number of transducers which, according to today's technique, is to be mounted at each measuring point, may vary and will be the subject matter of practical discussions, but sooner or later all of them will usually be used up and, thus, eventually a need for actual replacements will arise. Then, one has to resort to conventional replacement technique with the limitations, deficiencies and disadvantages involved therewith.